Aster yellows and swede midge – new threats to prairie canola production

The Challenge

Two new threats to canola production have surfaced in Western Canada, swede midge and aster yellows. Little is known about how either react in the Prairies, but aster yellows which is a disease vectored by leafhopper insects, infected fields in 2012 with rates reaching 82% infestation. Although swede midge has been a serious threat to crucifer production in Ontario for over a decade, it was first found in Saskatchewan in 2012.

The Project

Gain a better understanding of both new threats to canola production in the Prairies through the investigation of epidemiology, yield losses, outbreaks, and management.

The Results

Swede midge

• 113 out of 150 pheromone traps were returned from 2014 and 2015.
• Males were found in low numbers on pheromone traps from three locations in MB and 21 locations in SK. No swede midges were found on traps from AB and BC.
• Substantial expansion of range as 11 of the SK locations were outside the known distribution area
• Likely two generations of swede midge larvae that fed on canola on the prairies in 2014, with emergence of the first adults well into July.

Aster yellows (AY)

• AY 5-point rating system developed.
• Preliminary estimations of economic threshold under dry and moist conditions for AY on canola.
• Due to low incidence in plots, confirmation of resistance/tolerance germplasm was not possible.
• No AY infected leafhoppers have been found in traps set up in AB, MB and SK for the past three years, suggesting AY inoculation may come from migratory leafhoppers.

Grower Benefits

Insecticides are useful on swede midge, but due to its life cycle careful scouting and timing is required when the economic threshold is met. Currently there is no way to control aster yellows, but severity has significantly dropped after the outbreak in 2012.